Advances in molecular genetics have made it plausible to correct many heritable and acquired disorders by strategically placing corrected or correcting copies of the causative genes in patients with these types of disease, termed gene therapy. Expectations for gene therapy are great, this because of the considerable press generated by the many gene therapy trials (>100) in the United States and because every week disease are being defined at the genetic and molecular level. Unfortunately, to date every few patients have benefitted from gene therapy. This has led to harsh criticism of those who advocate gene therapy. Despite the criticisms gene therapy continues to have huge therapeutic potential. The genesis of this program project arose from our observation, in 1991, that the enthusiasm for the application of gene therapy was ahead of the science of the details. It was this anticipation that led to our proposing to bring definition to the potential as well the limitations of gene therapy with cells of the skin. Much has been learned; new as well as old challenges mark the field. The current state of understanding has caused us to not focus on a disease, rather it addresses those elements that are key to bringing gene therapy with cells of the skin to the clinic in the near future. The governing hypothesis directing this renewal is: gene therapy with cells of the skin can be successfully utilized on a broad range of diseases once there is an understanding of expression and non expression of transgenes introduced into cells of the skin. Four projects are directed at this governing hypothesis. The theme of Project 1 is to define the basis for the continued expression of transgenes by cells in vitro and loss in vivo, and to test the concept that immortalized genetic modified keratinocytes have therapeutic potential. The theme of Project 2 is to test the concept that keratinocytes bearing transgenes which over-express immunosuppressive factors can be used to develop a "universal" epidermal allograft. The theme of Project 3 is to understand mechanisms by which gene products are transported out of skin and targeted to tissues and to devise strategies to enhance the activity and persistence of therapeutic gene products. The theme of Project 4 is to develop proof of principle and establish the parameters of the external regulation of transgenes of genetically modified cells of the skin. These projects will be supported by: administrative, cell culture/tissue reconstruction and transgene Cores.